1. Field of the Invention
The present invention relates to a zoom lens that is advantageous in achieving a high zoom ratio. The present invention also relates to an image pickup apparatus equipped with a zoom lens, such as a video camera or a digital camera.
2. Description of the Related Art
Zoom lenses having, at least, a first lens unit having a positive refracting power, a second lens unit having a negative refracting power, a third lens unit having a negative refracting power, and a fourth lens unit having a positive refracting power that are arranged in order from the object side to the image side and move during zooming in such a way that they are located closer the to the object side at the telephoto end than at the wide angle end have been know from Japanese Patent application Nos. 10-48518 and 8-68941.
In these zoom lenses, the distance between the first lens unit and the second lens unit and the distance between the second lens unit and the third lens unit are larger at the telephoto end than at the wide angle end, while the distance between the third lens unit and the fourth lens unit is smaller at the telephoto end than at the wide angle end.
This way of movement of the lens units can contribute to a decrease in the overall length of the zoom lens at the wide angle end and facilitate achieving an adequate angle of view. In addition, having a higher negative refracting power of the composite system of the second lens unit and the third lens unit at the telephoto end than at the wide angle end is advantageous in achieving good optical performance and an adequate zoom ratio of the zoom lens.